Method and apparatus for defining basic resource unit for NB-IoT user equipment in wireless communication system

ABSTRACT

A method and apparatus for performing transmission in a wireless communication system is provided. A narrowband internet-of-things (NB-IoT) user equipment (UE) transmits a physical uplink shared channel (PUSCH) to a network by using a first resource unit, and transmits an acknowledgement/non-acknowledgement (ACK/NACK) to the network by using a second resource unit. The first resource unit for PUSCH transmission consists of a first number of resource elements (REs) within a first tone in frequency domain and a first time interval in time domain. The second resource unit for ACK/NACK transmission also consists of a second number of REs within a second tone in frequency domain and a second time interval in time domain. The second number is smaller than the first number.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/065,634, filed on Jun. 22, 2018, which is the National Stage filingunder 35 U.S.C. 371 of International Application No. PCT/KR2016/015327,filed on Dec. 27, 2016, which claims the benefit of U.S. ProvisionalApplication No. 62/271,299, filed on Dec. 27, 2015, 62/274,732, filed onJan. 4, 2016, 62/298,971, filed on Feb. 23, 2016 and 62/318,763, filedon Apr. 6, 2016, the contents of which are all hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for defining a basic resourceunit for a narrowband internet-of-things (NB-IoT) user equipment (UE) ina wireless communication system.

Related Art

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

In the future versions of the LTE-A, it has been considered to configurelow-cost/low-end (or, low-complexity) user equipments (UEs) focusing onthe data communication, such as meter reading, water level measurement,use of security camera, vending machine inventory report, etc. Forconvenience, these UEs may be called machine type communication (MTC)UEs. Since MTC UEs have small amount of transmission data and haveoccasional uplink data transmission/downlink data reception, it isefficient to reduce the cost and battery consumption of the UE accordingto a low data rate. Specifically, the cost and battery consumption ofthe UE may be reduced by decreasing radio frequency (RF)/basebandcomplexity of the MTC UE significantly by making the operating frequencybandwidth of the MTC UE smaller.

Narrowband internet-of-things (NB-IoT) is a low power wide area network(LPWAN) radio technology standard that has been developed to enable awide range of devices and services to be connected using cellulartelecommunications bands. NB-IoT is a narrowband radio technologydesigned for the IoT, and is one of a range of mobile IoT (MIoT)technologies standardized by the 3GPP. NB-IoT focuses specifically onindoor coverage, low cost, long battery life, and enabling a largenumber of connected devices.

For supporting NB-IoT efficiently, it may be required to define a basicresource unit for NB-IoT.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for defining abasic resource unit for a narrowband internet-of-things (NB-IoT) userequipment (UE) in a wireless communication system.

In an aspect, a method for performing transmission by a narrowbandinternet-of-things (NB-IoT) user equipment (UE) in a wirelesscommunication system is provided. The method includes transmitting aphysical uplink shared channel (PUSCH) to a network by using a firstresource unit, and transmitting an acknowledgement/non-acknowledgement(ACK/NACK) to the network by using a second resource unit. The firstresource unit consists of a first number of resource elements (REs)within a first tone in frequency domain and a first time interval intime domain. The second resource unit consist of a second number of REswithin a second tone in frequency domain and a second time interval intime domain. The second number is smaller than the first number.

In another aspect, a narrowband internet-of-things (NB-IoT) userequipment (UE) in a wireless communication system is provided. TheNT-IoT UE includes a memory, a transceiver, and a processor, coupled tothe memory and the transceiver, that controls the transceiver totransmit a physical uplink shared channel (PUSCH) to a network by usinga first resource unit, and controls the transceiver to transmit anacknowledgement/non-acknowledgement (ACK/NACK) to the network by using asecond resource unit. The first resource unit consists of a first numberof resource elements (REs) within a first tone in frequency domain and afirst time interval in time domain. The second resource unit consist ofa second number of REs within a second tone in frequency domain and asecond time interval in time domain. The second number is smaller thanthe first number.

Data or control transmission for NB-IoT UE can be performed efficientlyby using a new basic resource unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows structure of a radio frame of 3GPP LTE.

FIG. 3 shows a resource grid for one downlink slot.

FIG. 4 shows structure of a downlink subframe.

FIG. 5 shows structure of an uplink subframe.

FIG. 6 shows an example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 7 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 8 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 9 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 10 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 11 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention.

FIG. 12 shows an example of sub-ACK/NACK resource unit according to anembodiment of the present invention.

FIG. 13 shows another example of sub-ACK/NACK resource unit according toan embodiment of the present invention.

FIG. 14 shows another example of sub-ACK/NACK resource unit according toan embodiment of the present invention.

FIG. 15 shows an example of TDM between ACK/NACK transmission and datatransmission according to an embodiment of the present invention.

FIG. 16 shows a method for performing transmission by a NB-IoT UEaccording to an embodiment of the present invention.

FIG. 17 shows a wireless communication system to implement an embodimentof the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Techniques, apparatus and systems described herein may be used invarious wireless access technologies such as code division multipleaccess (CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), single carrier frequency division multiple access (SC-FDMA),etc. The CDMA may be implemented with a radio technology such asuniversal terrestrial radio access (UTRA) or CDMA2000. The TDMA may beimplemented with a radio technology such as global system for mobilecommunications (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). The OFDMA may be implemented with aradio technology such as institute of electrical and electronicsengineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20,evolved-UTRA (E-UTRA) etc. The UTRA is a part of a universal mobiletelecommunication system (UMTS). 3rd generation partnership project(3GPP) long term evolution (LTE) is a part of an evolved-UMTS (E-UMTS)using the E-UTRA. The 3GPP LTE employs the OFDMA in downlink (DL) andemploys the SC-FDMA in uplink (UL). LTE-advance (LTE-A) is an evolutionof the 3GPP LTE. For clarity, this application focuses on the 3GPPLTE/LTE-A. However, technical features of the present invention are notlimited thereto.

FIG. 1 shows a wireless communication system. The wireless communicationsystem 10 includes at least one evolved NodeB (eNB) 11. Respective eNBs11 provide a communication service to particular geographical areas 15a, 15 b, and 15 c (which are generally called cells). Each cell may bedivided into a plurality of areas (which are called sectors). A userequipment (UE) 12 may be fixed or mobile and may be referred to by othernames such as mobile station (MS), mobile terminal (MT), user terminal(UT), subscriber station (SS), wireless device, personal digitalassistant (PDA), wireless modem, handheld device. The eNB 11 generallyrefers to a fixed station that communicates with the UE 12 and may becalled by other names such as base station (BS), base transceiver system(BTS), access point (AP), etc.

In general, a UE belongs to one cell, and the cell to which a UE belongsis called a serving cell. An eNB providing a communication service tothe serving cell is called a serving eNB. The wireless communicationsystem is a cellular system, so a different cell adjacent to the servingcell exists. The different cell adjacent to the serving cell is called aneighbor cell. An eNB providing a communication service to the neighborcell is called a neighbor eNB. The serving cell and the neighbor cellare relatively determined based on a UE.

This technique can be used for DL or UL. In general, DL refers tocommunication from the eNB 11 to the UE 12, and UL refers tocommunication from the UE 12 to the eNB 11. In DL, a transmitter may bepart of the eNB 11 and a receiver may be part of the UE 12. In UL, atransmitter may be part of the UE 12 and a receiver may be part of theeNB 11.

The wireless communication system may be any one of a multiple-inputmultiple-output (MIMO) system, a multiple-input single-output (MISO)system, a single-input single-output (SISO) system, and a single-inputmultiple-output (SIMO) system. The MIMO system uses a plurality oftransmission antennas and a plurality of reception antennas. The MISOsystem uses a plurality of transmission antennas and a single receptionantenna. The SISO system uses a single transmission antenna and a singlereception antenna. The SIMO system uses a single transmission antennaand a plurality of reception antennas. Hereinafter, a transmissionantenna refers to a physical or logical antenna used for transmitting asignal or a stream, and a reception antenna refers to a physical orlogical antenna used for receiving a signal or a stream.

FIG. 2 shows structure of a radio frame of 3GPP LTE. Referring to FIG. 2, a radio frame includes 10 subframes. A subframe includes two slots intime domain. A time for transmitting one subframe is defined as atransmission time interval (TTI). For example, one subframe may have alength of 1 ms, and one slot may have a length of 0.5 ms. One slotincludes a plurality of orthogonal frequency division multiplexing(OFDM) symbols in time domain. Since the 3GPP LTE uses the OFDMA in theDL, the OFDM symbol is for representing one symbol period. The OFDMsymbols may be called by other names depending on a multiple-accessscheme. For example, when SC-FDMA is in use as a UL multi-access scheme,the OFDM symbols may be called SC-FDMA symbols. A resource block (RB) isa resource allocation unit, and includes a plurality of contiguoussubcarriers in one slot. The structure of the radio frame is shown forexemplary purposes only. Thus, the number of subframes included in theradio frame or the number of slots included in the subframe or thenumber of OFDM symbols included in the slot may be modified in variousmanners.

The wireless communication system may be divided into a frequencydivision duplex (FDD) scheme and a time division duplex (TDD) scheme.According to the FDD scheme, UL transmission and DL transmission aremade at different frequency bands. According to the TDD scheme, ULtransmission and DL transmission are made during different periods oftime at the same frequency band. A channel response of the TDD scheme issubstantially reciprocal. This means that a DL channel response and a ULchannel response are almost the same in a given frequency band. Thus,the TDD-based wireless communication system is advantageous in that theDL channel response can be obtained from the UL channel response. In theTDD scheme, the entire frequency band is time-divided for UL and DLtransmissions, so a DL transmission by the eNB and a UL transmission bythe UE cannot be simultaneously performed. In a TDD system in which a ULtransmission and a DL transmission are discriminated in units ofsubframes, the UL transmission and the DL transmission are performed indifferent subframes.

FIG. 3 shows a resource grid for one downlink slot. Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols in time domain. It isdescribed herein that one DL slot includes 7 OFDM symbols, and one RBincludes 12 subcarriers in frequency domain as an example. However, thepresent invention is not limited thereto. Each element on the resourcegrid is referred to as a resource element (RE). One RB includes 12×7resource elements. The number N^(DL) of RBs included in the DL slotdepends on a DL transmit bandwidth. The structure of a UL slot may besame as that of the DL slot. The number of OFDM symbols and the numberof subcarriers may vary depending on the length of a CP, frequencyspacing, etc. For example, in case of a normal cyclic prefix (CP), thenumber of OFDM symbols is 7, and in case of an extended CP, the numberof OFDM symbols is 6. One of 128, 256, 512, 1024, 1536, and 2048 may beselectively used as the number of subcarriers in one OFDM symbol.

FIG. 4 shows structure of a downlink subframe. Referring to FIG. 4 , amaximum of three OFDM symbols located in a front portion of a first slotwithin a subframe correspond to a control region to be assigned with acontrol channel. The remaining OFDM symbols correspond to a data regionto be assigned with a physical downlink shared chancel (PDSCH). Examplesof DL control channels used in the 3GPP LTE includes a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), a physical hybrid automatic repeat request (HARQ) indicatorchannel (PHICH), etc. The PCFICH is transmitted at a first OFDM symbolof a subframe and carries information regarding the number of OFDMsymbols used for transmission of control channels within the subframe.The PHICH is a response of UL transmission and carries a HARQacknowledgment (ACK)/non-acknowledgment (NACK) signal. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI includes UL or DL schedulinginformation or includes a UL transmit (TX) power control command forarbitrary UE groups.

The PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, a resource allocation of anupper-layer control message such as a random access response transmittedon the PDSCH, a set of TX power control commands on individual UEswithin an arbitrary UE group, a TX power control command, activation ofa voice over IP (VoIP), etc. A plurality of PDCCHs can be transmittedwithin a control region. The UE can monitor the plurality of PDCCHs. ThePDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel. The CCE corresponds to a plurality of resource element groups.

A format of the PDCCH and the number of bits of the available PDCCH aredetermined according to a correlation between the number of CCEs and thecoding rate provided by the CCEs. The eNB determines a PDCCH formataccording to a DCI to be transmitted to the UE, and attaches a cyclicredundancy check (CRC) to control information. The CRC is scrambled witha unique identifier (referred to as a radio network temporary identifier(RNTI)) according to an owner or usage of the PDCCH. If the PDCCH is fora specific UE, a unique identifier (e.g., cell-RNTI (C-RNTI)) of the UEmay be scrambled to the CRC. Alternatively, if the PDCCH is for a pagingmessage, a paging indicator identifier (e.g., paging-RNTI (P-RNTI)) maybe scrambled to the CRC. If the PDCCH is for system information, asystem information identifier and a system information RNTI (SI-RNTI)may be scrambled to the CRC. To indicate a random access response thatis a response for transmission of a random access preamble of the UE, arandom access-RNTI (RA-RNTI) may be scrambled to the CRC.

FIG. 5 shows structure of an uplink subframe. Referring to FIG. 5 , a ULsubframe can be divided in a frequency domain into a control region anda data region. The control region is allocated with a physical uplinkcontrol channel (PUCCH) for carrying UL control information. The dataregion is allocated with a physical uplink shared channel (PUSCH) forcarrying user data. When indicated by a higher layer, the UE may supporta simultaneous transmission of the PUSCH and the PUCCH. The PUCCH forone UE is allocated to an RB pair in a subframe. RBs belonging to the RBpair occupy different subcarriers in respective two slots. This iscalled that the RB pair allocated to the PUCCH is frequency-hopped in aslot boundary. This is said that the pair of RBs allocated to the PUCCHis frequency-hopped at the slot boundary. The UE can obtain a frequencydiversity gain by transmitting UL control information through differentsubcarriers according to time.

UL control information transmitted on the PUCCH may include a HARQACK/NACK, a channel quality indicator (CQI) indicating the state of a DLchannel, a scheduling request (SR), and the like. The PUSCH is mapped toa UL-SCH, a transport channel. UL data transmitted on the PUSCH may be atransport block, a data block for the UL-SCH transmitted during the TTI.The transport block may be user information. Or, the UL data may bemultiplexed data. The multiplexed data may be data obtained bymultiplexing the transport block for the UL-SCH and control information.For example, control information multiplexed to data may include a CQI,a precoding matrix indicator (PMI), an HARQ, a rank indicator (RI), orthe like. Or the UL data may include only control information.

In the current LTE specification, all UEs shall support maximum 20 MHzsystem bandwidth, which requires baseband processing capability tosupport 20 MHz bandwidth. To reduce hardware cost and battery power ofMTC UEs, reducing bandwidth is a very attractive option. To enablenarrowband MTC UEs, the current LTE specification shall be changed toallow narrowband UE category. If the serving cell has small systembandwidth (smaller than or equal to bandwidth that narrow-band UE cansupport), the UE can attach based on the current LTE specification.

For example, a MTC UE may operate in reduced UE downlink and/or uplinkbandwidth of 1.4 MHz (i.e. 6 PRBs), regardless of operating systembandwidth of a cell. A subband in which a MTC UE operates (i.e. MTCsubband) may be located in a center of the system bandwidth (e.g. center6 PRBs). Alternatively, multiple subbands in which multiples MTC UEsoperates may be allocated in one subframe for multiplexing of themultiple MTC UEs. In this case, the multiple UEs may use differentsubbands from each other, or, may use the same subband (not center 6PRBs).

Further, a MTC UE may operate in further reduced UE downlink and/oruplink bandwidth of 200 kHz (i.e. 1 PRB). This may be referred to as anarrowband internet-of-things (NB-IoT). Narrowband IoT (NB-IoT) mayprovide access to network services using physical layer optimized forvery low power consumption (e.g. full carrier bandwidth is 180 kHz,subcarrier spacing can be 3.75 kHz or 15 kHz). A number of E-UTRAprotocol functions supported by all Rel-8 UEs may not be used for NB-IoTand need not be supported by eNBs and UEs only using NB-IoT. In NB-IoT,the MTC UE may operate in a legacy cell which has a system bandwidthwider than 200 kHz with backward compatibility. This system may bereferred to as in-band NB-LTE. Alternatively, the MTC UE may operate ina frequency, in which the legacy cell does not exist and only for theMTC UE. This system may be referred to as stand-alone NB-LTE.

Coverage enhancement (CE) for the MTC UE is described. When a UEperforms initial access towards a specific cell, the UE may receivemaster information block (MIB), system information block (SIB) and/orradio resource control (RRC) parameters for the specific cell from aneNB which controls the specific cell. Further, the UE may receivePDCCH/PDSCH from the eNB. In this case, the MTC UE should have broadercoverage than the legacy UE. Accordingly, if the eNB transmitsMIB/SIB/RRC parameters/PDCCH/PDSCH to the MTC UE with same scheme as thelegacy UE, the MTC UE may have difficulty for receiving MIB/SIB/RRCparameters/PDCCH/PDSCH. To solve this problem, when the eNB transmitsMIB/SIB/RRC parameters/PDCCH/PDSCH to the MTC UE having coverage issue,the eNB may apply various schemes for coverage enhancement, e.g.subframe repetition, subframe bundling, etc.

When a MTC UE having coverage issue uses the same service in the samecell with a legacy UE or a MTC UE not having coverage issue, a largeamount of resources may be used to transmit data to the MTC UE havingcoverage issue. It may restrict services for other UEs. Therefore, inorder to avoid the problem that an operation for the MTC UE havingcoverage issue may interference an operation for other UEs, a timeregion for the MTC UE having coverage issue and a time region for otherUEs may be multiplexed by time division multiplexing (TDM). The timeregion for the MTC UE having coverage issue and time region for otherUEs may be multiplexed with a long-term period, e.g. tens of minutes, orwith a short-term period, e.g. some subframes.

Hereinafter, a MTC UE, a UE requiring coverage enhancement (CE), a lowcost UE, a low end UE, a low complexity UE, a narrow(er) band UE, asmall(er) band UE, a new category UE, a bandwidth reduced low complexityUE (BL UE), NB-IoT UE, or NB-LTE UE may have the same meaning, and maybe used mixed. Or, just a UE may refer one of UEs described above.Further, in the description below, a case where system bandwidth ofavailable cells is larger than bandwidth that new category narrowbandUEs can support may be assumed. For the new category UE, it may beassumed that only one narrow-band is defined. In other words, allnarrow-band UE shall support the same narrow bandwidth smaller than 20MHz. It may be assumed that the narrow bandwidth is larger than 1.4 MHz(6 PRBs). However, the present invention can be applied to narrowerbandwidth less than 1.4 MHz as well (e.g. 200 kHz), without loss ofgenerality. In these cases, the UE may be able to receive only a limitednumber of PRBs or subcarriers. Furthermore, in terms of UL transmission,a UE may be configured or scheduled with single or less than 12 tones(i.e. subcarriers) in one UL transmission to enhance the coverage byimproving peak-to-average power ratio (PAPR) and channel estimationperformance.

In NB-IoT, it is expected that different resource unit definition,compared to the conventional subframe or physical resource block, in DLand UL may be used. Hereinafter, a method for defining a basic resourceunit (hereinafter, just resource unit) for NB-IoT according toembodiments of the present invention is described.

First, a resource unit definition for PUSCH transmission according to anembodiment of the present invention is described. In PUSCH transmission,in order to allow reasonable transport block (TB) size carried in oneresource unit, a resource unit for NB-IoT may be considered. Oneresource unit may be one or some portion of one PRB in LTE, whichcorresponds to 14 OFDM symbols with 12 subcarriers. Regardless ofwhether the resource unit follows the same number of REs or not, theresource unit is expected to transmit one PUSCH.

In terms of resource unit definitions for PUSCH transmission, one of thefollowings may be considered.

(1) One TTI: The resource unit is used to schedule one TB. One TTI mayconsist of multiple resource units which may be spread over frequencyand/or time. TTI may be changed dynamically depending on the scheduledresource units in time domain. Or, TTI may be fixed by higher layerconfiguration.

Repetition may occur in TTI level. Minimum TTI size may be configured bythe network, and repetition may occur over minimum TTI. For example,minimum TTI size may be one resource unit. One resource unit may be adefault value for minimum TTI. If a UE is configured with larger numberof resource units than minimum TTI, repetition may occur continuouslyover the scheduled resource units. Otherwise, repetition may occur overminimum TTI. If scheduled resource units is smaller than the configuredminimum TTI size, repetition may occur over the scheduled resource unitsin continuous manner. If minimum TTI is configured, resource index maybe mapped within resource units in the minimum TTI. The total size ofresource index may be used for data scheduling. The minimum TTI may beconfigured per coverage class or per UE. The minimum TTI may also beconfigured to achieve time-diversity. When relatively larger minimum TTIis configured, latency may increase, but time-diversity gain may beachieved.

In case of control channel, minimum TTI or the number of resource unitsused for control channel multiplexing may also be considered. The numberof resource units used for control channel multiplexing is the size ofresource units where UEs can be multiplexed. The number of resourceunits may be jointly signaled with repetition number. Or, the number ofresource units may be inferred from transport block size (TBS). In otherwords, a UE may be dynamically indicted with the number of repetitions,and the UE may infer the number of resource units used in transmissionbased on TBS. For example, instead of indicating TBS index, actual TBsize may be signaled assuming the same code rate used. Or, a tableincluding code rate, TBS and the number of resource units may be used toindicate the resource unit size, code rate and TBS. The value range ofresource units may be [1 . . . N], where N may be 6 to accommodate 100bits. When minimum TTI is configured which is larger than one resourceunit, within one minimum TTI, the scheduled resource units may befurther indicated by the starting offset in resource units.

(2) One resource unit: This is similar to PRB in legacy system. Oneresource unit is the minimum resource block size where PUSCH can bescheduled. When single tone transmission is used, the number of bitstransmittable in legacy TTI length (1 ms) is very limited. Moreover,considering PAPR issue, if binary phase shift keying (BPSK) or pi/2 BPSKis used in single tone transmission, further restriction of bit size isexpected. Moreover, demodulation reference signal (DM-RS) in 1 ms (basedon legacy pattern) with single tone is very short. Thus, increasing thesize of resource in time (e.g. k ms) seems necessary. For example, whensingle tone is used for one resource unit, one resource unit may consistof single tone in k ms. Resource unit is used in resource allocation. Ifresource unit is multiple in frequency and time domains within one TTI,resource allocation may be jointly performed. Or, resource unit may beindexed from frequency first and then time second.

To be able to transmit reasonable TBS (e.g. minimum payload of Msg 3transmission), one resource unit may include at least about 168 REsusing BPSK and 84 REs using quadrature phase shift keying (QPSK),assuming minimum size of 56 bits. The size of k may be dependent on thenumber of DM-RS symbols in 1 ms. Assuming 4 OFDM symbols in 14 OFDMsymbols are used for DM-RS, k may be about 16 using BPSK and 8 usingQPSK. However, data mapping to allow symbol combining may be beneficialparticularly in deep coverage case. Moreover, it may reduce PAPR byrepeating the same data continuously. In that case, if p repetition isused for symbol combining, one resource unit may be multiple of p (i.e.k*p). This may be used only in case of BPSK is used or deep coveragecase.

In summary, a resource unit may consist of REs in m subcarrier within kms. In case of BPSK is used in single tone, k may be 16. Otherwise, kmay be 8. For other values of m (i.e. m=4, 8, 12), the k may be (2, 1,1), respectively.

FIG. 6 shows an example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. FIG. 6 correspondsto a case that subcarrier spacing is 3.75 kHz. Referring to FIG. 6 , oneresource unit for PUSCH transmission includes a single tone acrossmultiple subframes. Resource units are indexed from 0 to M−1.

FIG. 7 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. FIG. 7 correspondsto a case that subcarrier spacing is 15 kHz. Referring to FIG. 7 , oneresource unit for PUSCH transmission may include a single tone or twotones across multiple subframes. Resource units are indexed from 0 toL−1 by frequency first, and the remaining resource units are index fromL+N to L+N+L−2.

FIG. 8 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. Referring to FIG. 8, one TTI includes two resource units with single tone, two resourceunits with two tones and one resource unit with four tones. Resourceunit with single tone occupies 20 subframes, resource unit with twotones occupies 10 subframes, and resource unit with four tones occupies5 subframes. In this case, resource units within one TTI may be indexedby frequency first and time second principle.

FIG. 9 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. One TTI may includemultiple resource units and one TB may be scheduled over multipleresource units. In this case, continuous resource unit allocation infrequency or in tone may be desired with hopping. Accordingly, theresource units may be index from the smallest resource unit to thelargest resource unit. Referring to FIG. 9 , resource units are indexfrom resource units with single tone by frequency first and time second(0, 1, 2, 3 . . . ), and resource units with two tones by frequencyfirst and time second (2 k, 2k+1, 2 k+2, 2 k+3 . . . ), and resourceunits with four tones by frequency first and time second (3 k, 3k+1, 3k+2, 3 k+3 . . . ). Resource allocation may be based on contiguousallocation using compact format. In this case, the TB size schedulablein one TTI may be different based on number of tones used or number ofresource units scheduled.

Further, in order to minimize PAPR/cubic metric (CM), repetition mayoccur in symbol level, TTI level and/or resource unit levels. In thiscase, the resource mapping within one resource unit may consist ofmultiple symbol repetitions with multiple symbols.

Alternatively, resource units may be defined per number of tones, andresource units per each number of tones may be overlapped.

FIG. 10 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. Referring to FIG.10 , one resource unit for PUSCH transmission includes a single toneacross k ms. Resource units are indexed from 0 to L−1.

FIG. 11 shows another example of resource units for PUSCH transmissionaccording to an embodiment of the present invention. Referring to FIG.11 , one resource unit for PUSCH transmission includes two tones acrossk/2 ms. Resource units are indexed from 0 to L/2−1.

Referring to FIGS. 10 and 11 , when more than one tone is used for PUSCHtransmission, the length of resource unit in time may be adapted toinclude the same number of REs to carry the minimum TBS. That is, inFIG. 10 , a length of one resource unit with single tone in time is k,whereas, in FIG. 11 , a length of one resource unit with two tones intime is k/2.

The index of resource unit in frequency may be mapped per each number oftones, e.g. L resource units in frequency domain for single tone (L=12in 15 kHz subcarrier spacing, L=48 in 3.75 kHz subcarrier spacing).Different number of tones may be multiplexed by TDM A cell-specificconfiguration of {number of subcarriers, duration, periodicity, offset}may be configured (one or more parameters may be given with defaultvalues). Alternatively, Different number of tones may be multiplexed byFDM. A cell-specific configuration of {number of subcarrier/tones,number of resource units in frequency, starting tone index, end toneindex} may be configured. Hybrid of TDM and FDM may also be considered.

Depending on the number of available number of resource units infrequency domain, the size of resource allocation can be different. Toavoid the change of size of resource allocation, one resource unit maycover both time domain and frequency domain. For example, resource unitswithin L subcarriers in k ms may be used for resource allocation in acontinuous resource mapping manner. Alternatively, starting tone index,among L subcarriers which is the number of tones used for transmission,may be used. L may be semi-statically configured. In other words, whenone resource unit consists of multiple tones, resource unit may start inany tone index rather than fixed in a few tone indices.

Alternatively, the number of tones and starting tone index may bejointly indicated. Or, number of tones and the starting tone index maybe indicated separately. For example, if 4 bit is used for resourceallocation in frequency domain, one example is as follows. The followingexample may be applied to a case that the UE is configured with 15 kHzspacing. The following example may also support both single and multipletones. The bit size may be different if a UE is configured with 3.75 kHzsubcarrier spacing.

-   -   [0 0 0 0]=12 subcarriers are allocated    -   [0 0 0 1]=single tone is allocated (MSB=0), 2 bits except for        two most significant bits (MSBs) may be used for tone index (4        possible tone indices).    -   [1 0 0 0]=four tones are allocated (two MSB=1 0), 1 bit except        for the first three bits may be used for starting tone index (2        possible locations)    -   [1 1 1 0]=eight tones are allocated (two MSB=1 1), 1 bit except        for the first three bits may be used for starting tone index (2        possible locations)

Another example is that 0 to 11 may be allocated for starting subcarrierindex in single tone case, 12 to 21 to may be allocated in 3 tones case,and so on.

If a UE is configured with 3.75 kHz subcarrier spacing, multiple tonetransmission may also be configured. If a UE with 3.75 kHz subcarrierspacing is not be able to configured with multi tone transmission, theresource allocation may be common between 3.75 kHz and 15 kHz subcarrierspacing, and the total number of resource allocation entries cover 48entries where some are reserved for 15 kHz. If the UE is configured withmultiple tone transmission, depending on the subcarrier spacing insingle tone, resource allocation size for UL grant may be different.

However, in Msg3, it is important to have the same size between 3.75 kHzand 15 kHz subcarrier spacing for carrier carrying UL grant in randomaccess response (RAR), as a UE does not know which subcarrier spacing isused. For that, resource allocation between 3.75 kHz and 15 kHzsubcarrier spacing may be aligned, assuming both can be scheduled withmulti tone transmissions (e.g. 0 to 47 for single tone for startingsubcarrier index, 48 to 57 to 3 tone transmissions, and so on).

Alternatively, when 3.75 kHz is configured in Msg 3, the resourceallocation flexibility may be restricted, in which case the initialstarting subcarrier index may be configured in SIB per physical randomaccess channel (PRACH) resource set and only limited number ofsubcarrier indices may be dynamically indicated by UL grant in RAR. Forexample, the starting subcarrier index may be configured as 10 and theresource allocation may be dynamically selected from 10 to 21. This maybe useful in case of FDM among different coverage levels. Alternatively,the total required resource allocation states for single tone may be setas 66 with 3.75 kHz subcarrier spacing and 30 for 15 kHz subcarrierspacing. To reduce the bit size, it may be assumed that 2 states are notused in single tone with 3.75 kHz subcarrier spacing. For example, twostarting subcarrier indices with 3 (or 6) tones may not be supported ortwo starting subcarrier indices with single tone may not be supported.

In modulation and coding scheme (MCS)/TBS, the modulation of pi/2 BPSKor pi/4 QPSK in addition to code rate needs to be signaled. As pi/2 BPSKoffers lower spectral efficiency, it is suggested to add a few moreentries with pi/2 BPSK modulation schemes.

Another consideration for UL transmission may be scheduling window,which may be used to determine the starting time of any UL transmissionor only applicable to PUSCH data transmission.

Separate configuration per coverage level and/or per data or ACK/NACKmay be considered. In terms of indicating timing, it may be a multipleof scheduling window timing. The starting value may be larger than 8since the last subframe of control channel. In this case, if the gapbetween the last control channel repetition and the first subframe ofthe next scheduling window is less than 8, the index may be counted fromthe second next scheduling window. Otherwise, the gap may start from thefirst scheduling window. Alternatively, it may always be started fromthe first available scheduling window. In this case, the network may beresponsible to make it sure that the timing gap is greater than 8. Whenthe timing is less than the required processing time, a UE may dropPUSCH transmission (the similar behavior may be applied to otherchannels as well).

In terms of gap, it may be a multiple of scheduling window periodicity.Scheduling window may be configured with periodicity, offset and/orduration.

Alternatively, scheduling window may be implicitly determined by thesize of resource unit per number of tones. Starting from SFN=0 with slotindex 0, resource unit may be used implicitly for determining schedulingunit. This may allow UEs with the same number of tones scheduled beingaligned. Otherwise, the starting time of one UL transmission may not bealigned with resource unit size (in other words, it may start in anytime).

If aperiodic channel state information (CSI) is supported, twoapproaches may be considered.

(1) Option 1: Uplink control information (UCI) piggyback may besupported.

Aperiodic CSI may be triggered in DCI. If M=12, legacy piggybackmechanism may be used. Otherwise, UCI may be transmitted in the lastsubframe of resource unit, and the last subframe may be rate matched fordata transmission. One subframe may be used for transmitting UCI, andthe UCI may be encoded in a repetition coding with no CRC. In otherwords, different UL transmission using shortened resource unit may beused, and the last subframe may carry UCI similar to ACK/NACKtransmission mechanism (i.e. No CRC, repetition encoding, etc.). If onesubframe is too large, one slot may be used for UCI piggyback. Theoverall concept is not to support UCI piggyback per subframe, rather itmay be treated as if a separate transmission, where the resource interms of time/frequency may be shared with regular PUSCH transmission.

Another approach for UCI piggyback is that UCI may be added in the lastOFDM symbol of a resource unit. If multiple resource units arescheduled, the last resource unit may be used for UCI piggyback. This isto minimize the impact on data. If the last symbol is punctured due to,e.g. for SRS transmission, the second last OFDM symbol may be used forUCI piggyback. If the last symbol is not sufficient to transmit UCI withthe desired code rate (e.g. ⅓ repetition code), the second last OFDMsymbol may also be used. In other words, the mapping of UCI starts fromthe last OFDM symbol towards the earlier OFDM symbol. Another approachis that UCI may be mapped to a few OFDM symbols starting from the lastOFDM symbol, though the mapping starts from the earliest OFDM symbol intime domain. As tail-biting convolutional code (TBCC) is used,information may be carried in the first part of transmission. In thatsense, it may be desirable to puncture the last OFDM symbols to minimizethe impact on data transmission. Another approach is that a fixed numberof OFDM symbols may be reserved in a resource unit, and data may be ratematched if aperiodic CSI is triggered. For example, if 3 bits UCI istransmitted, totally 5 OFDM symbols may be assumed in case QPSK is used,and 10 OFDM symbols may be assumed in case pi/2 BPSK is used.

With the approach described above, in a single tone with pi/2 BPSK, thefirst OFDM symbol next/previous OFDM symbol to DM-RS may be reserved for10 slots (for pi/4 QPSK, 5 slots are assumed). For 3 tone transmissions,2 slots may be assumed. For 6 tone transmissions, 1 slot may be assumed.For 12 tone transmissions, 1 slot may be assumed. The remaining REs inthe OFDM symbol reserved for UCI may be used for data transmission.Otherwise, the UCI may be repeated in the same ODFM symbol. Differentbehavior from current procedure is to perform rate matching around UCIREs to minimize the impact on data transmission. To minimize the impact,OFDM symbols used for UCI may be placed in the end of resource units.

(2) Option 2: Similar to PDCCH order, a special setting to triggeraperiodic CSI may be used. UCI may be carried as a payload.

In terms of transmitting aperiodic CSI, either aperiodic CSI based onNB—RS may be used or RSRP measurement on the serving cell may bereported. If RSRP is reported, the value range may be large. For that,only PRACH CE level based on the RSRP measurement may be reported whichcan be done with 2 bits.

If UCI piggyback of CSI is used, the maximum bit size of CQI feedbackmay be 3 or 2 bits. UCI piggyback may be used to be carried overrepetition as well.

Another approach is that aperiodic CSI may always be transmitted with 12subcarriers with only legacy piggyback mechanism. This implies thatsingle tone transmission or less than 12 subcarriers may not support UCIpiggyback. Alternatively, legacy behavior may be used assuming thatmaximum RE of PUSCH is restricted for the scheduled PUSCH number oftones.

Second, a resource unit definition for ACK/NACK transmission accordingto an embodiment of the present invention is described. The followingshows some examples of the resource unit for ACK/NACK transmission.

(1) 12 subcarriers in 1 ms in DL and 1 subcarrier in X ms in UL: if thisresource unit is used, UL resource unit length is X times longer than DLresource unit length.

(2) K subcarriers in m ms in DL and 1 subcarrier in X ms in UL

(3) 1 subcarrier in 1 ms in both DL and UL

(4) K subcarriers in 1 ms in DL and 1 subcarrier in 1 ms in UL

Depending on the definition of the resource unit, the number of NB-IoTDL carriers, and the number of NB-IoT UL carriers capable of ACK/NACKtransmission, the number of UEs which can be multiplexed at the sametime on the same resource may be defined. For example, regardless of thedefinition of the resource unit, if the minimum size of scheduling ofPDSCH is 1 DL resource unit and the minimum size of transmission ofACK/NACK transmission is 1 UL resource unit, one of the followingoptions may be considered.

(1) Option 1: Only one UE may always be allocated to the resource forACK/NACK transmission corresponding to one PDSCH (1 bit transmission inone resource unit). In such case, if the first example of the definitionof the resource unit (i.e. 12 subcarriers in 1 ms in DL and 1 subcarrierin X ms in UL) or the second example of the definition of the resourceunit (i.e. K subcarriers in m ms in DL and 1 subcarrier in X ms in UL),FDM with other UL transmissions, such as other ACK/NACK transmission ordata transmission, may be considered.

(2) Option 2: Multiple UEs may be allocated to the resource for ACK/NACKtransmission, as 1 UL resource unit can accommodate more than oneACK/NACK transmissions. In such case, ACK/NACK for multiple UEs may bemultiplexed by code division multiplexing (CDM). Or, ACK/NACK formultiple UEs may be multiplexed by time division multiplexing (TDM) bydividing one UL resource unit into sub-ACK/NACK resource unit.

(3) Option 3: Smaller granularity of resource unit may be determined forACK/NACK transmission which is different from resource unit for datatransmission. Smaller granularity of resource unit may be referred to assub-ACK/NACK resource unit. In such case, ACK/NACK transmission maystart in the middle of one UL resource unit.

If option 2 or 3 described above is used, there may be multiple UEscorresponding to the same ACK/NACK transmission timing. In such case,for example, ceil (Max_Num_Subcarrier/K) or Max_Num_Subcarrier (whichcan be corresponding to the same NB-IoT UL carrier) may be multiplexedby either of CDM, TDM or frequency division multiplexing (FDM).

Option 3 will be described in detail. The question of the resource unitfor NB-IoT may be whether or not to use the same resource unit forACK/NACK transmission as data transmission. If the same resource unit isused for ACK/NACK transmission and data transmission, overall latencymay increase. For example, if single tone transmission is used, oneresource unit may be length of 12 or 10 or 40 or 20 or 8 ms (and 12subframes). In other words, the resource unit duration may be k ms, andk may be one of among {8, 10, 12, 20, 40}. In such case, if CDM amongdifferent ACK/NACK transmissions are not achieved, to transmit one bit,overall about 168 REs (or 168 repetitions) may be used. This type ofrepetition may be necessary only for UEs with extreme coverage. However,it may be very excessive for some UEs with relatively good coverage. Inthat sense, the basic resource unit may be defined based on coveragelevel. For example, if there are three coverage levels, the followingapproach (or similar approaches) may be used as an example or inprinciple.

(1) Coverage level 1: If CDM or multiplexing in the same resource amongmultiple UEs are not used, 1 ms with single or multiple tones may beassumed to be a sub-ACK/NACK resource unit. Since CDM is not used,selection of the sub-ACK/NACK resource unit may be used to multiplexmultiple UEs. Depending on resource of control channel (to schedule DLtraffic) or resource of DL transmission, the resource for ACK/NACKtransmission may be selected.

For one of mapping mechanisms, the resource for ACK/NACK transmissionmay be selected based on starting (E)CCE or starting index of controlchannel transmission. If CCE or multiplexing of different controlchannels are used, the starting resource index of control channel may beused to select the sub-ACK/NACK resource unit within one resource unit.

FIG. 12 shows an example of sub-ACK/NACK resource unit according to anembodiment of the present invention. Referring to FIG. 12 , in one PUSCHresource unit, there are multiple sub-ACK/NACK resource units, and eachof the sub-ACK/NACK resource units are selected based on CCE index.

FIG. 13 shows another example of sub-ACK/NACK resource unit according toan embodiment of the present invention. Referring to FIG. 13 , ifmultiple tones are available for ACK/NACK transmission, the resource maybe determined from the lowest (or highest) tone index) and then move tothe next tone.

Alternatively, ACK/NACK resources may be mapped from the frequency firstand time next. In this case, the maximum number of tones usable forACK/NACK transmission resource needs to be configured in prior viahigher layer signaling or predefined. Alternatively, ACK/NACK resourcesmay be mapped based on location (in terms of time or frequency) ofstarting transmission of data channel. Alternatively, ACK/NACK resourcesmay be mapped based on a gap between control channel and data channel.For example, if control channel indicates the gap between two channelsfor better TDM multiplexing, the gap may be used to determine the timeresource or sub-ACK/NACK resource unit index within one PUSCH resourceunit. Alternatively, ACK/NACK resources may be mapped based on UE-ID orsome other higher layer configuration.

(2) Coverage level 2: Similar mechanism as coverage level 1 may beconsidered. However, in coverage level 2, the sub-ACK/NACK resource unitmay be larger than that of coverage level 1. To allow multiplexing, thesame sub-ACK/NACK resource unit may be used regardless of coveragelevel. In this case, some repetition may be necessary which occur inPUSCH resource unit (i.e. discontinuous repetition across PUSCH resourceunits).

(3) Coverage level 3: Similar mechanism as coverage level 1 may beconsidered. Also, the same resource unit size as PUSCH resource unit maybe used. In this case, similar mechanism to schedule PUSCH may beconsidered. For example, explicit time resource may be dynamicallyindicated from DCI.

In order to allow efficient channel estimation and reasonable amount ofresource, one resource unit for multiplexing multiple ACK/NACKtransmissions may be determined as follows. If a single tone is used forACK/NACK transmission, m*k subframes may be one resource unit. m is thenumber of subframes used for one sub-ACK/NACK resource unit. Forexample, m=4, k=12. If repetition or more than m REs are needed forACK/NACK transmission for a UE, repetition across resource units areused. If multiple tones are used for ACK/NACK transmission, min (r,m)*floor (m/floor (12/1))*k subframes may be one resource unit. r is thenumber of minimum repetition in a coverage level. In other words,different size of resource unit may be used per coverage level.

FIG. 14 shows another example of sub-ACK/NACK resource unit according toan embodiment of the present invention. Referring to FIG. 14 , one tone(sub-ACK/NACK resource unit) in each side within 180 kHz may be reservedfor ACK/NACK transmission. When frequency for ACK/NACK transmission isreserved, slot hopping or subframe hopping or multiple-subframes hoppingmay be considered. Given that only single tone is used for ACK/NACKtransmission and the number of REs for DM-RS is also limited,multiple-subframes hopping rather than slot level hopping or subframelevel hopping may be preferred. If frequency hopping is used, 2*m*12 REsare used for one ACK/NACK transmission in one ACK/NACK resource unit.Repetition may occur across ACK/NACK resource units. There may bemultiple PUSCH resource units corresponding to one ACK/NACK resourceunit. Furthermore, depending on the number of tones used for PUSCHtransmission, the shorter resource unit size in time may be used. Insuch case, more PUSCH resource units may be formed within one ACK/NACKresource unit. Furthermore, if 3.75 kHz is used for ACK/NACKtransmission, the duration becomes about 4× times. In this case, morePUSCH resource units may be formed within one ACK/NACK resource unit.The ACK/NACK transmission may start at the first ACK/NACK resource unitafter k ms since the last subframe of PDSCH transmission or lastsubframe of last PDSCH resource unit where PDSCH is transmitted. In FDD,k=4.

Hereinafter, various aspects of ACK/NACK transmission by using the newresource unit according to an embodiment of the present invention willbe described below.

(1) TDM of ACK/NACK Transmission and Data Transmission

When resource unit for ACK/NACK transmission is smaller than resourceunit for data transmission (i.e. either option 2 or option 3 describedabove), the usable ACK/NACK resource to allow possible UE multiplexingmay be multiplexed via FDM or TDM. When FDM is used for ACK/NACKresource multiplexing, to restrict the impact on scheduling of PUSCH,some TDM restriction of ACK/NACK resource may be considered.

For example, a few subframes in the beginning and the ending of Msubframes may be reserved for ACK/NACK transmission, whereas othersubframes may be used for K resource units for PUSCH transmission. Forexample, M=40 and one UL resource unit is 1 subcarrier*12 subframes. 3UL resource unit may be used for PUSCH transmission and remainingsubframes, i.e. each of 2 subframes in the beginning and ending, may beused for ACK/NACK transmission. In terms of timing, ACK/NACKtransmission may occur in the first available ACK/NACK subframe after ksubframe since the last transmission of DL data.

When multiple NB-IoT UL carriers are used, different ACK/NACK resourcesand data multiplexing per UL carrier may also be configured. From a UEperspective, if a UE hops across different NB-IoT UL carriers, theresource multiplexing between ACK/NACK and data may be aligned acrossNB-IoT UL carriers.

Considering potentially variable DL traffic volumes (or UL/DL ratio) perapplications or depending on time (e.g. firmware update requires heavyDL), K number of UL resource units may be configured between ACK/NACKresources. K may be 0, 1, 2, . . . Max K. It may be assumed that oneACK/NACK resource contains at least m subframe (e.g. m=2) in time. Byadjusting or configuring K, the number of ACK/NACK resource may beadjusted depending the DL traffic. If necessary, repetition may occur inconsecutive ACK/NACK resource subframes. The number m can be larger than2, e.g. 4 or 8, considering multiple-subframe channel estimation and I/Qcombining.

K may be configured by the network via SIB signaling or higher layersignaling or via MIB. K may be a cell-specific value or coverage levelspecific value. K may also be UE-specific value. When K is configured,ACK/NACK resource may start from SFN=0 with subframe index=0, unless anyoffset is configured to start ACK/NACK resource. When K is configuredper coverage level, the number m may be also different per coverageclass, and also be configured per coverage class. If K is configured bycell-specifically, the number m may also be configured bycell-specifically. In other words, K and m may be configured together.Also, the usable number of tones may be configured. As default value, itmay be assumed that 12 (for 15 kHz subcarrier spacing) and 48 (for 3.75kHz subcarrier spacing) are usable by ACK/NACK transmission for FDM. Incase of 3.75 kHz, some other default value considering frequency reuseless than 1 may also be considered.

FIG. 15 shows an example of TDM between ACK/NACK transmission and datatransmission according to an embodiment of the present invention.Referring to FIG. 15 , in the first NB-IoT UL carrier, two UL resourceunits are configured between ACK/NACK resources. A total of 4 subframesoccupy ACK/NCK resources in M subframes. In the second NB-IoT ULcarrier, ACK/NACK resources occupy each of 2 subframes in the beginningand ending of each M subframes, i.e. total of 4 subframes.

(2) FDM of ACK/NACK Transmission and Data Transmission

When TDM among multiple UEs for ACK/NACK transmissions are used, FDM ofACK/NACK resource and PUSCH resource may be considered. If more than onesub-ACK/NACK resource unit is needed for ACK/NACK transmission due torepetition, the repetition may occur continuously or discontinuously.Repetition may occur continuously starting from the first sub-ACK/NACKresource unit in case of continuous repetition. In this case, thecollision among different UEs needs to be addressed by the networkscheduling to avoid collision. Alternatively, repetition may occur inresource unit level, and multiple UEs may be multiplexed by usingdifferent sub-ACK/NACK resource unit. Considering that it is likely thatDL transmissions among multiple UEs may also be multiplexed by TDMrather than FDM, continuous repetition may work.

When multiple NB-IoT UL carriers are used for NB-IoT UL transmissionwith FDM between ACK/NACK transmission and data transmission, ACK/NACKresource may be configured in multiple NB-IoT UL carriers rather thanper NB-IoT carrier to allow more data resources. For example, ACK/NACKresource may be configured in every ‘m’ number of NB-IoT UL carrier atedge of ‘m’ NB-IoT UL carriers. Or, only one ACK/NACK resource may beconfigured in multiple configured NB-IoT UL carriers. Also, the numberof subcarriers/tones usable for ACK/NACK resources may be configured aswell (e.g. from 1 to a few subcarriers). The configuration may be givenby SIB. If ACK/NACK resource is configured across more than one NB-IoTUL carrier, frequency retuning may be necessary to switch from oneNB-IoT UL carrier to another NB-IoT UL carrier. When retuning is neededwithin one ACK/NACK transmission with repetition, some retuning latencymay be considered by puncturing retuning gaps or not utilizing a slot orsubframe.

Further, when FDM of ACK/NACK transmission and data transmission isused, TDM may be used for DL transmissions among multiple UEs indifferent coverage class. In this case, ACK/NACK transmission amongmultiple UEs in TDM may be desirable. In terms of control channel, themaximum repetition level R may be defined per coverage class, and a UEmay monitor multiple repetition numbers, such as R/4, R/2, R. Thecontrol channel may be transmitted with different repetition number anda UE may monitor multiple starting subframes/instances within onemonitoring occasion which is defined by the maximum repetition level R.ACK/NACK transmission may start at n+k (e.g. k=4), and n is the lastsubframe where PDSCH is transmitted.

If FDM between data transmissions of multiple UE is used, some type ofmultiplexing among multiple ACK/NACK transmissions may be necessary. FDMamong multiple ACK/NACKs may be considered aligned with datamultiplexing.

(3) Collision Handling Between ACK/NACK Transmission and DataTransmission Via Scheduling

For data and ACK/NACK resource sharing, multiplexing among PUSCH andPUCCH may be done based on scheduling. ACK/NACK may be transmitted inany resource by using FDM or TDM or CDM and the collision between PUSCHand ACK/NACK transmission may be avoided by the network scheduling. Inthis case, the resource used for ACK/NACK transmission and/or datatransmission including frequency and time information may be indicateddynamically. Time information may include delay between UL grant and theactual UL transmission (for data transmission case) and/or between thelast subframe of PDSCH transmission and actual ACK/NACK transmission(for ACK/NACK transmission case). If scheduling is used for multiplexingof ACK/NACK resource and data resource, the subcarrier index or toneindex of ACK/NACK resource may be indicated dynamically in DL grant, inorder to avoid potential collision. In this case, the timing may bedetermined implicitly. The subcarrier index or tone index of ACK/NACKresource may be indicated from a subset of tones/subcarriers usable forACK/NACK transmission. Tones/subcarriers usable for ACK/NACKtransmission may be semi-statically configured per UE or per cell. Theconcept may be similar to ACK/NACK resource indictor (ARI).

(4) Hybrid of TDM and FDM

In terms of resource allocation or multiplexing between ACK/NACKtransmission and data transmission, hybrid approach of (1) and (2) maybe considered. In other words, for configuring ACK/NACK resource, atleast one of the followings may be considered.

-   -   Periodicity of ACK/NACK resource    -   Duration of ACK/NACK resource in one period (i.e. how many        subframes or resource units may be used for ACK/NACK resource in        each period)    -   Offset of ACK/NACK resource    -   Number of subcarriers used for one ACK/NACK transmission    -   Number of total subcarriers usable for ACK/NACK transmission (or        the offset in frequency where PUSCH should not be mapped)

The configuration may be given per coverage class, and/or per NB-IoT ULcarrier and/or per legacy UL carrier and/or the total NB-IoT UL carriersand/or per UE.

FIG. 16 shows a method for performing transmission by a NB-IoT UEaccording to an embodiment of the present invention. The embodiments ofthe present invention described above may be applied to this embodimentof the present invention.

In step S100, the NB-IoT UE transmits a PUSCH to a network by using afirst resource unit. In step S110, the NB-IoT UE transmits ACK/NACK tothe network by using a second resource unit. The first resource unitconsists of a first number of REs within a first tone in frequencydomain and a first time interval in time domain. The second resourceunit consist of a second number of REs within a second tone in frequencydomain and a second time interval in time domain. The second number issmaller than the first number.

The first resource unit may correspond to the PUSCH resource unitdescribed above. The first resource unit may carry a minimum TBS fortransmission of the PUSCH. A number of the first tone may be one. Inthis case, the first resource unit may consist of the first number ofREs within a single tone in frequency domain and 8 ms in time domain.The single tone may correspond to a single 15 kHz subcarrier.Alternatively, a number of the first tone may be more than one. In thiscase, the first time interval in time domain may be adapted to includethe first number of REs according to the number of the first tone. Thefirst resource unit may consist of the first number of REs within 12tones in frequency domain and 1 ms in time domain. The first resourceunit may be defined per number of the first tone, and a same RE may beincluded in each of the first resource unit per number of the firsttone.

The second resource unit may correspond to sub-ACK/NACK resource unitdescribed above. The second resource unit may be allocated to ACK/NACKtransmission of one UE. The second resource unit may correspond toACK/NACK transmission of one PDSCH. A number of second tone may be one.The second resource unit may be allocated at middle of the first unit.An index of the second tone may be indicated from a subset of tonesusable for ACK/NACK transmission.

FIG. 17 shows a wireless communication system to implement an embodimentof the present invention.

An eNB 800 includes a processor 810, a memory 820 and a transceiver 830.The processor 810 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 810. Thememory 820 is operatively coupled with the processor 810 and stores avariety of information to operate the processor 810. The transceiver 830is operatively coupled with the processor 810, and transmits and/orreceives a radio signal.

A UE 900 includes a processor 910, a memory 920 and a transceiver 930.The processor 910 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 910. Thememory 920 is operatively coupled with the processor 910 and stores avariety of information to operate the processor 910. The transceiver 930is operatively coupled with the processor 910, and transmits and/orreceives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The transceivers 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method performed by a network node in a wireless communication system, the method comprising: transmitting, to a user equipment (UE), information for a number of repetitions of one or more first resource units and information for a number of repetitions of one or more second resource units; receiving, from the UE, uplink (UL) data on the one or more first resource units repetitively used by the number of repetitions of the one or more first resource units; and receiving, from the UE, an acknowledgement/negative-acknowledgement (ACK/NACK) signal on the one or more second resource units repetitively used by the number of repetition of the one or more second resource units, wherein each of the one or more first resource units consists of a first number of resource elements (REs) within one or more subcarriers in frequency domain and a first time interval in time domain, wherein each of the one or more second resource units consists of a second number of REs within a single subcarrier in frequency domain and a second time interval in time domain, and wherein the second number of REs is smaller than the first number of REs.
 2. The method of claim 1, wherein the one or more first resource units carry a minimum transport block size (TBS) for transmission of a physical uplink shared channel (PUSCH).
 3. The method of claim 1, wherein a number of the one or more subcarriers is one.
 4. The method of claim 3, wherein the one or more first resource units consist of the first number of REs within a single subcarrier in frequency domain and 8 ms in time domain.
 5. The method of claim 3, wherein the one or more first resource units consist of the first number of REs within a single 15 kHz subcarrier in frequency domain and 8 ms in time domain.
 6. The method of claim 1, wherein a number of the one or more subcarriers is more than one.
 7. The method of claim 6, wherein the first time interval in time domain includes the first number of REs according to the number of the one or more subcarriers.
 8. The method of claim 6, wherein the one or more first resource units consist of the first number of REs within 12 subcarriers in frequency domain and 1 ms in time domain.
 9. The method of claim 1, wherein the one or more first resource units are defined for each of the one or more subcarriers, and wherein a same number of REs is included in each of the one or more first resource units.
 10. The method of claim 1, wherein the one or more second resource units are allocated to ACK/NACK transmission of a UE.
 11. The method of claim 1, wherein the one or more second resource units are related to ACK/NACK transmission of a physical downlink shared channel (PDSCH).
 12. The method of claim 1, wherein the one or more second resource units are allocated in a middle of the one or more first resource units.
 13. The method of claim 1, wherein an index of the single subcarrier is indicated from a subset of subcarriers usable for ACK/NACK transmission.
 14. A network node in a wireless communication system, the NB-IoT UE comprising: a memory; a transceiver; and at least one processor, coupled to the memory and the transceiver, the processor configured to: control the transceiver to transmit, to a user equipment (UE), information for a number of repetitions of one or more first resource units and information for a number of repetitions of one or more second resource units; control the transceiver to receive, from the UE, uplink (UL) data on the one or more first resource units repetitively used by the number of repetitions of the one or more first resource units; and control the transceiver to receive, from the UE, an acknowledgement/negative-acknowledgement (ACK/NACK) signal on the one or more second resource units repetitively used by the number of repetition of the one or more second resource units, wherein each of the one or more first resource units consists of a first number of resource elements (REs) within one or more subcarriers in frequency domain and a first time interval in time domain, wherein each of the one or more second resource units consists of a second number of REs within a single subcarrier in frequency domain and a second time interval in time domain, and wherein the second number of REs is smaller than the first number of REs.
 15. A method performed by a user equipment (UE) in a wireless communication system, the method comprising: receiving, from a network, information for a number of repetitions of one or more first resource units and information for a number of repetitions of one or more second resource units; transmitting, to the network, uplink (UL) data using the one or more first resource units repetitively by the number of repetitions of the one or more first resource units; and transmitting, to the network, an acknowledgement/negative-acknowledgement (ACK/NACK) signal using the one or more second resource units repetitively by the number of repetitions of the one or more second resource units, wherein each of the one or more first resource units consists of a first number of resource elements (REs) within one or more subcarriers in frequency domain and a first time interval in time domain, wherein each of the one or more second resource units consists of a second number of REs within a single subcarrier in frequency domain and a second time interval in time domain, and wherein the second number of REs is smaller than the first number of REs.
 16. The method of claim 15, wherein the one or more first resource units carry a minimum transport block size (TBS) for transmission of a physical uplink shared channel (PUSCH).
 17. The method of claim 15, wherein the one or more first resource units consist of the first number of REs within a single subcarrier in frequency domain and 8 ms in time domain.
 18. The method of claim 15, wherein the first time interval in time domain includes the first number of REs according to the number of the one or more subcarriers.
 19. The method of claim 15, wherein the one or more first resource units consist of the first number of REs within 12 subcarriers in frequency domain and 1 ms in time domain.
 20. The method of claim 15, wherein the one or more first resource units are defined for each of the one or more subcarriers, and wherein a same number of REs is included in each of the one or more first resource units. 